Developmental language delays and language disorders are a relatively common developmental finding in children. A review of the current literature indicates a persistence of language delays in a percentage of children. Language disorders may persist across the lifespan, and symptoms may change over time. The lack of consistency in the terminology and classification systems related to developmental language disorders impacts research and clinical practice.
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• Developmental language disorders are not uncommon, and they have some long-term impacts on the lives of the individuals.
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• A language disorder may occur in the presence of other conditions such as hearing impairment, intellectual disabilities, developmental disabilities, autism spectrum disorder, attention deficit hyperactivity disorder, traumatic brain injury, or psychological/emotional disorders.
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• No clear etiology has been found for developmental language disorders, but there is much interest in finding a gene or genes that affect language development. Multifactorial etiology, clinical heterogeneity, and differential diagnosis of primary and secondary language disorders make management more complex.
Historical note and terminology
Developmental language disorders have been examined in the literature for some time, but no consistent definition or classification system has been used across studies. Developmental language disorders are distinguished from other conditions by a language deficit that results in problems with comprehension, production, or usage of language. When a language disorder is the primary disability with no comorbidities such as sensory impairment, intellectual disability, global developmental delay, motor dysfunction, autism spectrum disorder, or attention deficit hyperactivity disorder, it is considered a developmental language disorder.
One classification of communication disorders was based on clinical, functional, or anatomical features and associated findings. One of the categories in this classification, developmental speech disorder syndrome, included a wide variety of disorders ranging from mild delays in articulation and language development to severe comprehension difficulties and lack of speech development. No further differentiation was made, and this was a diagnosis of exclusion (58).
The fourth edition of the Diagnostic and Statistical Manual of Mental Disorders classified developmental language disorders as communication disorders and included the categories of expressive language disorder, mixed receptive-expressive language disorder, phonological disorder (formerly developmental articulation disorder), and communication disorder not otherwise specified (02). Each of these disorders must interfere with academic or occupational achievement or with social communication. Expressive language disorder and mixed receptive-expressive language disorder were defined by a discrepancy between nonverbal intelligence and language abilities. Communication disorders may coexist with mental retardation, speech-motor or sensory deficit, or environmental deprivation, but the difficulties are in excess of those usually associated with these problems.
Although attempts to classify preschool language disorders have focused on the global nature of the disordered language (receptive, expressive, mixed), other attempts to classify developmental language disorders have focused on the nature of the spoken language deficit (99; 98). Further subgroupings include phonologic-syntactic disorders that display both phonologic disturbances (omissions, substitutions, and distortions of consonants and consonant clusters in speech) and syntactic impairment evidenced by lack of small words and absence of word endings. Oromotor dysfunction may be seen in these disorders whereas comprehension, semantics, pragmatics, and prosody are relatively spared. Verbal auditory agnosia is characterized by an absence of auditory comprehension and little or no expressive speech. Patients with semantic-pragmatic disorders are fluent but are impaired in comprehension and show deficits in using the rules that govern the use of language in social contexts. The lexical-syntactic syndrome is marked by poor syntactic skills and difficulty finding words. Paraphasia is seen, but pragmatics, phonology, and comprehension are relatively spared.
The DSM-V (Diagnostic and Statistical Manual of Mental Disorders, 5th edition) has moved back to a broader categorization of communication disorders (03). The category of communication disorders includes language disorder, speech sound disorder, childhood onset fluency disorder (stuttering), social (pragmatic) communication disorder, and other specified and unspecified communication disorders. The unspecified diagnostic code is appropriate when further evaluation is needed (03). Speech includes articulation, fluency, voice, and resonance quality. Language includes the form, function, and use of a conventional system of symbols in a rule-governed manner for communication. The subcategory of language disorders now includes significant delays or functional difficulties in either expressive or receptive language for various forms of communication, including, but not limited to, written and spoken communication. Social (pragmatic) communication disorder addresses difficulty using language appropriately in a social context. DSM-5 criteria for communication disorders do not require a minimum level of nonverbal cognitive ability (83).
International standard diagnostic classification codes from the World Health Organization’s (WHO) International Classification of Diseases, Tenth Revision (ICD-10) are used to identify diagnosis and health conditions, including specific disorders of speech and language, in public health and health care settings. Public schools in the United States do not use the ICD for diagnosis. Students are identified and qualified for special education services by the Individuals with Disabilities Education Act of 2004 (IDEA) (144). Fifty-three percent of speech language pathologists in the United States are employed in schools, and 90% of speech language pathologists working in schools serve children with diagnoses of language disorders.